Presentation on theme: "NETWORKS – DATA TRANSMISSION. Vocabulary Review Protocol Agreed set of rules Data packet Envelope of data sent across a network Contains Source address."— Presentation transcript:
NETWORKS – DATA TRANSMISSION
Vocabulary Review Protocol Agreed set of rules Data packet Envelope of data sent across a network Contains Source address Destination address Sequence # Timestamp Data itself And more!
Why does data transmission speed vary? Download and upload speed/bandwidth of the client Download and upload speed/bandwidth of the server Amount of traffic across the network Your local network The ISP’s network The Internet itself Demand for the network or web resource It takes longer to access something that is being accessed by everybody
Transmission Media/Medium Metal conductors Ethernet cables Coaxial cables Phone lines Fiber optics Made from glass or plastic Example: FIOS Wireless (i.e. radio waves)
Transmission Media Characteristics Speed Reliability Cost Security Evaluate each of the transmission medias.
Transmission Media/Medium MediumSpeedReliabilityCostSecurity Metal Conductors FastGoodMost expensive OK Fiber OpticsFastestGoodCheapest cable, but more expensive equipment OK WirelessSlower b/c of noise and interference Not as good because of noise, distance, and interference Air is freeEncryption and password necessary to secure network
What is data compression? Taking data and packaging it to a smaller size Examples of data compression: ZIP (archives multiple files and uses some compression) JPEG - images MP3 - audio H.264 – video (e.g. Blu-ray, YouTube)
Why is data compression used to transmit across a network? Compress / shrink the size of a file Transfer is faster because the data is smaller
Lossy vs. Lossless Compression Lossy compression original quality CANNOT be reconstructed when decompressed (mp3, jpg) ality_comparison_jpg_vs_saveforweb.jpg ality_comparison_jpg_vs_saveforweb.jpg Loss-less compression original quality CAN be reconstructed when decompressed (png, flac, zip)
Circuit-switched vs. Packet-switched Networks Circuit-switched Network Example: Phone Network ngNetworks.htm ngNetworks.htm t_a_Bell_System_Telephone_Switchboard_( ).jpg t_a_Bell_System_Telephone_Switchboard_( ).jpg What are the problems with circuit-switched networks? Packet-switched Network Example: The Internet
Packet Switching Break data up into packets & transmit Individual packets are not all necessarily transmitted through the same links Each packet travels over the best available link at the time Packets may arrive at destination out of order must be re-ordered and reassembled